Different tracking arrangements exist for tracking a moving object, such as, for example, a hunting dog. One may attach to a dog, for example, a radio transmitter the analog signal transmitted by which is monitored with an appropriate directional antenna. With this arrangement, one is able to detect the direction of the dog and, on the basis of the level of a received signal, to make an assessment, even though not a very accurate one, on how far away the dog with its radio transmitter is. The described arrangement has disadvantages. If there exist several separate objects being tracked in the same area, tracking devices may disturb each other. This happens, for example, when two or more devices use the same frequency in tracking. The frequency band assigned to different tracking systems varies from one country to another. Thus, this situation is not rare in such countries in which the used frequency band is narrow and there is a considerable number of users. In addition, the continuous on-mode of the transmitter consumes the power of the battery of the transmitter, and thus its operating time is limited with one charging.
Also known is a tracking solution which utilises GPS (Global Positioning System) locating and a GSM (Global System for Mobile communications) network. In this tracking method, the GPS locator is at least in the device carried by the dog being tracked. The transmitter carried by the dog transmits the result of location performed by means of the GPS either as an SMS (Short Message Service) message or a data call to the tracker's device via a conventional GSM network. The tracker's device may also utilise a map base describing the area, in which case the location of the dog being tracked may be indicated with said map.
The system may function in several modes. First, it may function with a call principle, in which case the tracker transmits a locating call. To this, the device carried by the object being tracked responds with an SMS message which includes location data. This arrangement is not totally real-time, but the tracker has either the result of previously performed location in his/her use, or the tracker will have to perform a new location which requires time.
Tracking may also be periodic, in which case location data are transmitted after a defined time has elapsed. Each tracking result is communicated by using a data call.
Tracking may also be area-specific, in which case if the object being tracked stays within a defined area, no location data are communicated.
If one wishes to communicate location data to several tracking devices at the same time, one has to transmit for each tracking device either its own SMS message or connect a data call connection. SMS messages are always charged on the basis of transmitted messages. Thus, in this tracking arrangement, the “continuous tracking” of the object is relatively expensive, because one has to pay a price defined by the operator for messages communicated of each transmitted location data.
A problem of continuous tracking is mainly the power consumption of the terminal carried by the object being tracked. The charge in the terminal battery will not be sufficient for long, if the data transmission connection is continuously on. The requirement is thus to transmit location data only when someone requires it, but then as real-time and continuously as possible. Also the GPS locator consumes plenty of the charge in the terminal batteries, and thus its continuous on-mode essentially shortens the operating time of the terminal. The worst possible situation is that the device has poor reception and the connection breaks off after a locating request. Then, it is possible that the terminal keeps transmitting location data with full power to an unattainable user and, because of this, the power of the battery of the terminal runs down fast.